The present invention relates to motor vehicle sensors and actuators.
Modern motor vehicles are equipped with numerous sensors which provide detailed information regarding the operation of the vehicle. This information may be displayed for a driver or it may be processed and provided to various vehicle control systems. A target wheel sensor, for example, may be used to determine the angular speed or angular position of a rotating part in the vehicle, e.g., a crankshaft and a driveshaft. In either case, a target wheel may be engaged with the rotating part for inducing signals in one or more sensors positioned next to the target wheel, with the signals representing the angular position or angular speed of the rotating part. These signals can be used in various control systems, e.g., an ignition system and a speed control system.
The present invention recognizes that certain applications require the detection of not only the position of the target wheel, but the detection of the direction of motion of the target wheel as well. Devices have been provided that can be used to detect the position of the target wheel and the direction of motion. These devices typically require a first sensor and a second sensor placed at a predetermined angular distance from each other around a target wheel. Unfortunately, the need for a second sensor, and thus, a second coil, increases the cost of the device.
The present invention has recognized these prior art drawbacks, and has provided the below-disclosed solutions to one or more of the prior art deficiencies.
A target wheel sensor assembly includes a target wheel, one magnet, and one sensing element placed there between. The magnet and the sensing element are configured so that as the target wheel rotates it causes the sensing element to output an asymmetric signal.
In one aspect of the present invention, the sensor assembly defines a central axis, and the magnet and the sensing element are oriented perpendicular to the central axis. In this aspect, the magnet generates a magnetic field that is oriented at an angle with the central axis. Preferably, the angle is in a range of twenty degrees to seventy degrees (20xc2x0-70xc2x0).
In another aspect of the present invention, the sensor assembly defines a central axis, and the magnet is oriented perpendicular to the central axis. In this aspect, the magnet generates a magnetic field that is oriented parallel to the central axis. Moreover, the sensing element is oriented at an angle with the central axis. Preferably, the angle is in a range of zero degrees to seventy degrees (0xc2x0-70xc2x0).
In yet another aspect of the present invention, the sensor assembly defines a central axis, and the magnet and the sensing element are oriented perpendicular to the central axis. The magnet generates a magnetic field that is oriented parallel to the central axis. In this aspect, the magnet is centered on the central axis, and the sensing element is placed a distance from the central axis. The magnet defines a length and preferably, the distance is in a range of forty percent to one hundred percent (40%-100%) of one-half of the length.
In yet still another aspect of the present invention, the sensor assembly defines a central axis. The magnet defines a long axis and generates a magnetic field that is oriented perpendicular to the long axis. Moreover, the sensing element is oriented parallel to the long axis of the magnet. In this aspect, the magnet and the sensing element are oriented at an angle with the central axis. Preferably, the angle is in a range of one degree to forty degrees (1xc2x0-40xc2x0).
In another aspect of the present invention, the sensor assembly includes a magnetic piece placed near the magnet. The magnetic piece is configured so that as the target wheel rotates, it causes the sensing element to output an asymmetric signal.
In still another aspect of the present invention, the sensor assembly defines a central axis. In this aspect, the magnet defines a lower surface that is oriented perpendicular to the central axis and an upper surface that is oriented at an angle with the central axis.
In yet another aspect of the present invention, the magnet generates a first magnetic field and a second magnetic field. Preferably, the magnetic fields have different strengths.
In yet still another aspect of the present invention, a target wheel sensor assembly includes a target wheel, one magnet placed near the target wheel, and one sensing element placed between the target wheel and the magnet. In this aspect, the sensing element senses a position of the target wheel and a direction of motion of the target wheel as the target wheel rotates.
The present invention will now be described, by way of example, with reference to the accompanying drawings, in which: